This invention relates to the feed of fasteners, and more particularly to the variable pitch feed of fasteners.
A common fastener for tagging or attaching items is of the kind shown and described, for example, in U.S. Pat. No. 3,380,122. The fasteners are in an assemblage including a connecting bar, a plurality of coplanar connecting stubs extending from the connecting bar, a cross bar angularly disposed on each stub, a filament extending from each cross bar, and, typically, a head attached to each filament. Common fastener attaching apparatus, such as is shown and described for example in U.S. Pat. No. 4,416,407 are designed to install fasteners disposed at a unique distance, relative to each other, on the connecting bar. Typically, a feed wheel is provided having circumferential teeth matable with the assemblage stubs, operable to advance the assemblage in the apparatus. The number and pitch of the feed wheel teeth correspond to the pitch, or relative separation, of fasteners on the assemblage. However, fasteners are provided in varieties, for which it is common practice to have a different fastener dispensing apparatus for each variation.
Accordingly various attempts have been made to provide for feeding, in a single apparatus, of different assemblages, each having a unique pitch. Japanese publication No. 48939 dated 5/2/81 shows a fastener installation apparatus including a feed member having cooperative feeding and anti-back-up members. In one embodiment, an advance mechanism includes a U-shaped rod, the rod ends engagable with an installed fastener assemblage. In an alternative embodiment, two rods engage the assemblage. In each embodiment, an upper rod acts to advance the assemblage, and a lower rod serves to prevent upward movement of the assemblage during feeding. Both rods may bend in either direction, however, each rod end is provided with an angled upper surface so that downwards movement of the assemblage is favored. The feeding strength of this apparatus is limited by the resiliency, or biasing strength, of the upper rod. As the strength of the upper rod is increased, so too must the strength of the lower rod be increased, otherwise, the assemblage will back-up as the upper rod is urged upwardly. As a result, advancing strength is dissipated by the lower rod. Thus only a small advancing force can be generated by this design. Therefore, this apparatus is vulnerable to misfeeding and jamming, particularly where the assemblage fails to slide smoothly within the guide grooves of the apparatus.
U.S. Pat. No. 4,461,417 shows an apparatus designed to install fastener assemblages of varying pitch. A claw is pivotally mounted to a vertically moveable cam plate, the claw being biased in the direction of the connecting bar. A stationary claw with downwardly angled teeth is provided for the purpose of preventing upward movement of the connecting bar during feeding. In operation, the cam plate is raised, causing the claw to be dragged upwardly along the connecting bar. When the trigger is released, the cam plate is lowered, wherein the claw, or in an alternative embodiment, the teeth, engage the connecting bar and urge the assemblage downwardly. Since the claw is not drawn away from the connecting bar, an upwards force is exerted upon the connecting bar. A disadvantage to this design resides in the pivotal arrangement of the claw. As the cam plate is raised, the claw is pressed with continually greater force against the connecting bar, raising the potential for a jam. As the cam plate is lowered, the claw does not contact the connecting bar until the claw has pivoted into position, thus the connecting bar may not be advanced sufficiently to position the next fastener for ejection. Additionally, the design depends on the claw or teeth cutting into the connecting bar. Since fastener assemblages are fabricated from a wide variety of materials, there exists the possibility that the claw will either imbed itself too deeply into the connecting bar, causing a jam, or will fail to engage, resulting in a misfeed.
In a third approach, taken in U.S. Pat. No. 4,465,218, a tooth is moveably mounted within a pivotable base. The tooth is biased in the direction of the assemblage, pivoting on a pin. To prevent the tooth from overextending, a pin extends from the base into an aperture located near the tooth. When the trigger is depressed, the base pivots urging the tooth upwards. The tooth is caused to pivot, deflecting around the next stem. When the trigger is released the tooth engages the stem and urges the assemblage downwards. One disadvantage of this design is that all of the advancing and biasing force is exerted upon a small pivot pin which is subject to wear and breakage. Another disadvantage is that the design requires two carefully mated parts which must be assembled, thus raising the cost of the apparatus.
To prevent back-up of the assemblage during feed, the '218 patent provides a tooth biased in the direction of the assemblage. The tooth has an upper profile disposed at an angle to the axis of the assemblage, thus permitting downwards movement. A lower profile is disposed perpendicular to the axis of the assemblage, thus preventing upward movement of same. A problem with this design is that the device provides for only a fixed stub thickness. A thicker stub would not fit beneath the lower profile. A thinner stub could move up or down below the lower profile. As a result, the push rod, or plunger, may not squarely engage the cross bar, and thus jamming can arise. Additionally, this design does not permit the fastener assemblage to be withdrawn without additional devices for retracting the anti-back-up member.
It is therefore an object of the invention to provide a reliable variable pitch fastener installation apparatus.
It is a further object of the invention to provide for high strength advancing of the fastener assemblage.
It is an additional object of the invention to provide for secure positioning of the fastener to be ejected, while simultaneously preventing unwanted back-up of the assemblage during feeding.
It is another object of the invention to provide for simple and easy removal of a fastener assemblage.
It is yet another object of the invention to provide a fastener installation apparatus of relatively very low cost, incorporating a small number of parts, which functions with great reliability.
It is an additional object of the invention to provide for reliable assemblage feeding and positioning, despite significant variations in materials and dimensions in the fasteners installed.